The present invention relates to an oral pharmaceutical composition of isotretinoin containing at least two excipients, one of them being hydrophilic (i.e. having an HLB value superior or equal to 10), the other being an oily vehicle.
Isotretinoin (13-cis retinoic acid or 13-cis vitamine A), its isomers and some of its analogs are widely known to have a therapeutical activity in the treatment of several severe skin disorders like cystic acne, hypertrophic lupus erythematosus, keratinization disorders. Some evidences have also been brought about the activity of isotretinoin in basal cell carcinoma and squamous cell carcinoma.
Unfortunately, isotretinoin is also a highly toxic drug. Indeed, although isotretinoin, which is a cis derivative, is known to be less toxic than all trans vitamine A derivatives, side effects resulting from its use such as headache, vomiting, irritation of mucosa and liver toxicity, occur frequently. Furthermore, isotretinoin is known to be highly teratogenic in both animals and humans.
In order to well understand the interest of this invention, it is important to briefly summarize the physico-chemical pharmacokinetic properties. Isotretinoin is a reddish-orange powder. It is decomposed in presence of light and atmospheric oxygen. Isotretinoin is very poorly soluble in water what mades its bioavailability quite low after an oral intake (25% in fasted conditions and 40% in fed conditions). The maximum concentration (Cmax) is reached after 24 hours, while the (Cmax) of the active metabolite, 4-oxo-isotretinoin is reached after 6 hours. The elimination half-life of isotretinoin is of 7 to 37 hours while the half life (t1/2) of the active metabolite is of 11 to 50 hours. The steady-state concentrations of isotretinoin are reached after 1 week of treatment.
Very few publications and/or patents about the pharmaceutical formulation of isotretinoin are available. The drug is available on most markets under the form of a soft gelatine capsule containing a fatty liquid formulation of isotretinoin.
The U.S. Pat. No. 4,464,394 describing for the first time the therapeutical use of isotretinoin also describes briefly some possibilities of compositions including it. It involves the use of one antioxidant agent and of one carrier like lactose, starches or polyethyleneglycols.
The EP patent 0184942 describes more specific compositions of isotretinoin involving the use of one antioxidant, one chelating agent, one pharmaceutical carrier and one suspending agent. The composition obtained is stable during time.
The U.S. Pat. No. 4,545,977 relates to improved compositions of isotretinoin wherein taurine is associated with isotretinoin to reduce the side effects thereof.
The U.S. Pat. No. 5,716,928 describes a method for increasing bioavailability and for reducing inter and intra individual variability of an orally administered hydrophobic pharmaceutical compound, which comprises orally administering the pharmaceutical compound with an essential oil or essential oil component in an amount sufficient to provide greater bioavailability of the active ingredient.
The U.S. Pat. No. 6,028,054 relates to a method for increasing bioavailability of an orally administered hydrophobic pharmaceutical compound to human, which comprises orally administering the pharmaceutical compound concurrently with a bioenhancer comprising an inhibitor of e-cytochrome P450 3A enzyme or an inhibitor of P-glycoprotein mediated membrane transport.
The U.S. Pat. No. 5,993,858 describes a self microemulsifying excipient formulation for increasing the bioavailability of a drug which includes an emulsion including an oil or other lipid material, a surfactant and an hydrophilic co-surfactant.
What is not described is a composition of isotretinoin containing at least two lipid materials, one of them being hydrophilic. The said composition may be a suspension, emulsion or microemulsion.